Lime kiln

“ With the remainder of my outfit we cleaned out and sealed off the walls of an old lime kiln, which had served ever since the first rock buildings rose on Las Palomas. The oven was cut in the same porous formation, the interior resembling an immense jug, possibly twelve feet in diameter and fifteen feet in height to the surface of the ledge. By locating the kiln near the abrupt wall of an abandoned quarry, ventilation was given from below by a connecting tunnel some twenty feet in length. ”

“ The presence of a limey earth, however, mixed through the mass, is a positive advantage, as in this intimate admixture, the lime forms, under the heat of the kiln, a chemical combination with the other ingredients; and, as it melts more readily than some of them, it hastens the burning and makes it more complete. What is known as plastic clay, (one of the purest of the native clays,) is too strong for tile-making, and must be "tempered," by having other substances mixed with it, to give it a stiffer quality. ”

“ In order to show the prospective development of that which in the time of Simonds & White was an infantile industry, it may be stated that the capacity of the draw kiln is from 70 to 100 barrels of lime every twenty-four hours, while that of the square kiln is about 400 barrels per week. The draw kiln is more 237 expensive in construction than the other, but its capacity is greater, and it is not necessary to extinguish the fire, the lime being drawn out as it is burned and fresh stone put in. ”

“ Four brick kilns have been excavated. The one shown had five firing chambers. Roofing tiles were also made in the Jamestown brick kilns.
A 17th-century lime kiln excavated at Jamestown. In it oyster shells from the James River were burned for making lime. The iron hoops which supported the arched top of the kiln buckled from the intense heat. ”

“ This stone is in great request for hearth-stones, and the beds of ovens; and in lining of lime-kilns it turns to good account, for the workmen use sandy loam instead of mortar, the sand of which fluxes, and runs by the intense heat, and so cases over the whole face of the kiln with a strong vitrified coat-like glass, that it is well preserved from injuries of weather, and endures thirty or forty years. When chiseled smooth, it makes elegant fronts for houses, equal in colour and grain to Bath stone; and superior in one respect, that, when seasoned, it does not scale. ”

“ Thorough grinding and mixing are of the utmost importance, as otherwise the cement ultimately produced will be unsound and of inferior quality. The drying of the slurry is generally effected by the waste heat of the kilns, so that while one charge is burning another is drying ready for the next loading of the kilns. The kilns commonly employed are “chamber kilns,” circular Loading the kiln. structures not unlike an ordinary running lime kiln, but having the top closed and connected at the side with a wide flue in which the slurry is exposed to the hot products of combustion from the kiln. ”

“ The rotation of the kiln keeps the 'mix' in constant motion as it passes through the kiln, when it is first dried, then deprived of its carbonic acid and then vitrified or partially fused in such manner as to insure the proper chemical reaction between the basic lime and the acid silica, alumina and iron. Only that skill that is determined by experience can direct the burning at such a temperature that the continuous operation of the kilns will result in a clinker that is neither underburned nor overburned. ”

“ The better or peculiar kinds of bricks, as well as tiles of all kinds, are burnt in kilns instead of clamps. These kilns, though of a peculiar form, according to the purpose to which they are applied, yet do not differ in principle from the lime-kiln, &c. In the kiln, the fire is not intermixed with the bricks, but is applied beneath; nor are ashes mingled with the clay of which kiln-burnt bricks are made. ”

“ If this is not the case, the burnt lime is greyish in colour, from the finely divided particles of carbon, which, of course, spoils the lime for colour-making. The defects existing in lime burned in the above type of kiln originate in the irregular character of the product. It will be evident that the limestone lumps that are nearest the fire will be far more strongly heated than those in the upper part of the dome; and when calcined lime is kept incandescent for a long time, it becomes so compact in texture that it quenches with great difficulty when brought in contact with water. ”

“ These stones, when decomposed by heat, made a very strong quicklime, at least as pure as if it had been produced by the calcination of chalk or marble. Mixed with sand the lime made excellent mortar. The result of these different works was, that, on the 9th of April, the engineer had at his disposal a quantity of prepared lime and some thousands of bricks.
Without losing an instant, they began the construction of a kiln to bake the pottery, which was indispensable for their domestic use. They succeeded without much difficulty. ”

“ These colours, when they are carefully laid on stucco still wet, do not fade but are permanent. This is because the lime, having had its moisture burned out in the kiln, becomes porous and loses its strength, and its dryness makes it take up anything that may come in contact with it. On mixing with the seeds or elements that come from other substances, it forms a solid mass with them and, no matter what the constituent parts may then be, it must, obviously, on becoming dry, possess the qualities which are peculiar to its own nature. ”

“ The mortar, used in laying bricks and common stone, has a greater proportion of sand, which is generally of an inferior quality. Besides, the materials are incorporated with less care. Lime for the purposes of building is procured chiefly by calcining limestone in a kiln, with wood, coal, or some other combustible substance. It is also obtained by burning chalk, marble, and marine shells. Water poured upon newly-burnt or quick lime, causes it to swell, and fall to pieces into a fine powder. ”

“ The particular form in which lime should be applied for the best results depends upon the nature of the soil. In practice the proximity to chalk pits or lime kilns, the cost of the lime and cartage, will determine which is most economical. Generally speaking light poor lands deficient in organic matter will need the less caustic form or chalk, while quicklime will be most satisfactory on the stiff clays and richer soils. On the stiff soils overlying the chalk it was formerly the custom to dig pits through the soil to the rock below. ”

“ The kiln, of course, is for coal, and our stone requires about three-quarters of a ton per 100 bushels of lime, but this, I am told, varies according to quality, some requiring more than others; the quantity can best be determined by experimenting; also the regulation of the heat--if too great it will cause the stones to melt or run together as it were, or, if too little, they will not be properly burned. The business requires skill and judgment to run it successfully. ”

“ After they have provided their ore, their first work is to calcine it, which is done in kilns, much after the fashion of our ordinary lime kilns; these they fill up to the top with coal and ore untill it be full, and so, putting fire to the bottom, they let it burn till the coal be wasted, and then renew the kilnes with fresh ore and coal. ”

“ Although limestone containing a certain amount of clay can be burned in the kiln, it yields an inferior lime that is of little use to the builder owing to its low binding power. Marl of a certain composition finds an important application in the manufacture of hydraulic lime or cement.
The only kind of marl suitable for pigment is that111 containing clay with very little colour; and this is of somewhat rare occurrence, because most marls contain sufficient ferric oxide to give them a yellow shade. ”

“ The marble was all burnt into perfect, snow-white lime. But on its surface, in the midst of the circle,—snow-white too, and thoroughly converted into lime,—lay a human skeleton, in the attitude of a person who, after long toil, lies down to long repose. Within the ribs—strange to say—was the shape of a human heart.
“Was the fellow’s heart made of marble?” cried Bartram, in some perplexity at this phenomenon. “At any rate, it is burnt into what looks like special good lime; and, taking all the bones together, my kiln is half a bushel the richer for him.”
So saying, the rude lime-burner lifted his pole, and, letting it fall upon the skeleton, the relics of Ethan Brand were crumbled into fragments. ”

“ Any repairs can also be at once done to any one of the chambers as it gets emptied in its turn. In every process of treating clay or marl, with a view to drying it in the open air or to burning it, it is absolutely necessary to carry out these operations gradually at the risk of cracking and splitting the goods. This kiln, from its very gradual action and absence of sudden changes of temperature, produces no “wasters” from these causes, and the bricks can also be burnt in a much more moist state than in ordinary kilns, as the heat is very gradually brought to bear upon them. ”

“ They are then coated with the white clay called Kudaru-yama-tsuchi, for the double purpose of imparting to the finished vase a pure, soft aspect, and providing a ground suited to the blue, intense or delicate, which is used in the decoration. The piece is now placed in the preparatory kiln, called Suyaki-yama (kiln for unglazed ware) . The management of temperature in this kiln is a business demanding great care, the object being, not to bake the porcelain thoroughly, but merely to prepare it for the reception of the decoration and the glaze. ”

“ It can easily be argued that there would have been more in the 18th century, though no kiln sites have yet been [Pg 106] found. These considerations cannot be ignored, and consequently we must carefully avoid the trap of attributing all 18th-century, lead-glazed earthenwares made from Tidewater clay to the Rogers factory. A wood-fired Yorktown kiln burning pottery made from Peninsula clay and coated with a clear lead glaze would produce wares possessing variations of texture and color similar to those emerging from a comparable kiln, say, at Williamsburg. ”

“ All that night the fire is watched and fed, as it must be kept at the requisite temperature, for if it gets low, or, as the potters say, “slips,” the glaze is spoiled and the pottery must all be reglazed and fired again. The weather affects the kiln, the draught not being so good on a damp or rainy day as on a fair one; and the coal also must be specially chosen for the kiln. It takes several tons to fire one kiln, so that the success or failure of a firing is no light matter. ”

“ Three kinds of kilns are used in Illinois for burning bricks—beehive, tunnel, and scove. A beehive kiln (fig. 21) has a round base and a dome-shaped top and somewhat resembles an oversized beehive. Unfired bricks are stacked in the kiln and the doors are sealed with burned bricks and clay. Fires are started in hearths or fire boxes in the wall of the kiln and the heat is circulated into and through the kiln. It usually takes several days to fire the bricks adequately and let the kiln cool so that the bricks can be removed. ”

“ In these kilns the flames rush in at the fire holes, play on the built-up bungs of saggars, and escape through the top vent. In a two chamber kiln, as sometimes used for porcelain, the glaze is put in the lower chamber to receive the hottest fire, the biscuit in the upper getting a gentle fire. Where the fire enters directly into the kiln in any large volume, bags or small chimneys are built up inside the mouths to save the saggars from the worst of the fire. Of late the single-chamber, down-draught kiln has come into favour, as it is easily packed and economical of heat. ”

“ Kilns are of two types, open and muffle. In the open kiln the flames pass through the firing chamber and the ware may be exposed to their action, as in stoneware and brick; or it may be enclosed in the fire-clay cases, called saggers, as in the many forms of pottery, dishes or faience. The muffle kiln is a closed chamber which is surrounded by flames but which is not entered by them. These kilns are used in the manufacture of terra cotta and heavy enamel wares, and the portable kilns made for studio use are of this type. ”

“ The only furnace or kiln which we have tried with any degree of success, is the kiln used by the potters who make brown stone. It is called the 36-hole kiln. Wood is the fuel used in it. They burn billets before and under it, where there is an oven or arch pierced by 36-holes, through which the flame ascends into the chamber which contains the ware, and goes out at as many holes of the same dimensions in the crown of the furnace. The safeguards at bottom stand on knobs of clay, which won’t melt, about two inches square, and two inches and a half or three inches high ”

“ The hills which surround Ching–tê Chên are rich in the materials required by the potters, china clay and china stone of various qualities, fireclay for the seggars (cases to protect the porcelain in the kiln) , or for mixing in the coarser wares, and numerous other minerals. There was water–power which could be used in the mills for crushing and refining the minerals, and abundant wood for firing. Although coal is worked nowadays not many miles away, the potters still adhere to the wood, which has served their kilns from time immemorial. ”